Semiconductor device manufacturing processes include a liquid treatment process using a chemical liquid. In some cases, an organic solvent is used as the chemical liquid. For example, the liquid treatment process may be a pre-wet process that supplies an organic solvent to a surface of a semiconductor wafer (hereinafter referred to simply as “wafer”) before supplying a resist solution (See JP2007-299941A, for example). An organic solvent also may be used in a developing process.
Recently, circuit patterns have become finer and finer. It is thus expected that ultra-small foreign matters (e.g., particles) may affect adversely the device yield. Such particles may be foreign matters which are originally included in the organic solvent, or foreign matters or ionized metals which are originated from the transport passage materials and mixed into the organic solvent during transportation from a solvent tank through a passage.
Improving the cleanliness of a treatment liquid to be supplied to the wafer may be one possible measure for reducing an amount of particles remaining on a wafer after completion of a wet process (liquid treatment process). The cleanliness of a treatment liquid may be improved by optimizing the filtering condition, or by repeating cycle filtration. However, the filtration rate often must be set to be the same as the process liquid supply rate, and thus cannot be set to be an optimum value. Since there is a trade-off between the throughput of the filter and the filtration accuracy of the filter, it is difficult to determine an optimum filtering condition that meets both the filtration accuracy and the supply rate of the filtered treatment liquid per unit time which are required for the liquid treatment process.